Single-Substrate Pressure Sensor with Etching Stop Layer
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Solution Overview
Problem
Existing pressure sensors, particularly capacitance pressure sensors, require two substrates for manufacturing, leading to increased costs, larger size, and more complex manufacturing processes, with electrodes needing to be formed on both substrates.
Innovation Solution
A pressure sensor is designed with a single substrate featuring a reference pressure chamber and a diaphragm, where the diaphragm is formed as part of the substrate, and an etching stop layer prevents substrate material etching, allowing for a sealed reference pressure chamber and precise diaphragm thickness control, enabling relative pressure detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two substrates are bonded to manufacture a pressure sensor, then the sensor can be manufactured with conventional techniques, but the manufacturing cost increases and the sensor volume enlarges
Solution Approach 1:
The patent merges the functions of two separate substrates into a single substrate. The first substrate integrates both the diaphragm portion and the reference pressure chamber portion, eliminating the need for bonding two substrates together. This reduces manufacturing complexity and cost while maintaining sensor functionality.
Solution Approach 2:
The single substrate is segmented into functional regions: a diaphragm portion that responds to pressure and a reference pressure chamber portion that provides a reference pressure. This segmentation allows different functional areas to coexist on one substrate without requiring separate substrates.
2Reliability
If two substrates are bonded to manufacture a pressure sensor, then the sensor can be manufactured, but the manufacturing process becomes more complex with additional steps
Solution Approach 1:
The patent combines the manufacturing process into a single substrate workflow, eliminating substrate bonding steps. The diaphragm and reference pressure chamber are formed in sequence on the same substrate using standard semiconductor fabrication techniques, simplifying the overall manufacturing process.
3Measurement precision
If electrodes are formed on both substrates for a capacitance pressure sensor, then the sensor can detect pressure, but the manufacturing cost and process complexity increase
Solution Approach 1:
The patent merges the electrode structure into a single substrate configuration. One electrode is formed on the diaphragm portion and another electrode is formed on the reference pressure chamber portion, both on the same substrate. This maintains the capacitance detection capability while reducing the number of components.
4Device complexity
If a single substrate is used with a diaphragm and reference pressure chamber, then manufacturing cost is reduced, but the reference pressure chamber needs to be sealed
Solution Approach 1:
The patent applies preliminary action by forming a seal structure before final assembly. An embedding material is deposited to fill and seal the through-hole in the reference pressure chamber portion, creating a hermetic seal that traps the reference pressure. This preliminary sealing action ensures reliability before the sensor is completed.
5Productivity
If isotropic etching is performed to form the reference pressure chamber, then the chamber can be formed efficiently, but the diaphragm thickness must be precisely controlled
Solution Approach 1:
The patent applies preliminary action by forming an etching stop layer at a predetermined depth before performing isotropic etching. This stop layer acts as a barrier that prevents the etchant from penetrating through the diaphragm, ensuring precise thickness control while allowing efficient isotropic etching of the reference pressure chamber.
Solution Approach 2:
The etching stop layer serves as an intermediary element between the etchant and the diaphragm. It mediates the etching process by allowing the etchant to reach the reference pressure chamber region while blocking further etching that would compromise the diaphragm thickness, thus enabling both efficient etching and precise thickness control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces manufacturing costs, miniaturizes the sensor, improves sensitivity, and reduces sensitivity dispersion by allowing for precise formation of the diaphragm and reference pressure chamber without the need for bonding two substrates, while enabling efficient pressure detection.
Implementation Method 1
an etching stop layer which is formed on a surface of the diaphragm facing the reference pressure chamber
Implementation Method 2
an embedding material which is arranged in the through-hole
Data Source
AI summary
[Subject] To provide a pressure sensor capable of implementing cost reduction and miniaturization.[Solving Means] A pressure sensor 1 includes a silicon substrate 2 provided therein with a reference pressure chamber 8, a diaphragm 10, consisting of part of the silicon substrate 2, formed on a surface layer portion of the silicon substrate 2 to partition a reference pressure chamber 8, and an etching stop layer 9 formed on a lower surface of the diaphragm 10 facing the reference pressure chamber 8. A through-hole 11 communicating with the reference pressure chamber 8 is formed on the diaphragm 10, and a filler 13 is arranged in the through-hole 11.